I have several curtain rod holes in my kitchen French doors that need to be repaired & painted.
I would suggest epoxy putty, my favorite repair tip. I use it for repair- rehab in crafting and home improvement=the Oatey epoxy putty stick
I find it easier to work with than bondo and this clay like putty can be sculpted. It does harden in a few minutes and will dry a gray color can be sanded or drilled and will needing painting unless its final gray color works for your repair.
It's a two-part epoxy sticky-found at big box hardware stores in the plumbing department near the pvc purple glue. In a clear plastic red capped tube. I get mine at Lowes $6. Home Depots version and JB Weld is more $ and smaller. Other smaller 2 part epoxy sticks options can alsobe found in the boat marine and wood repair shopping sections.
You mix -press -then you can use scrape off excess (I use depleted gift card) and/or sand and paint. Cured putty is strong enough to drill through.
If you can find where the water leak is on your outside fountain you can use flex seal. I know that it's an infomercial and they have the tape that works underwater they had spray and a paint and it works fabulously. Good luck
I was going to say you can use bondo or even spackling, but if you can find the product Vimarhonor suggested, I'd definitely go with that. If not, give bondo a go.
SteelStik https://www.jbweld.com/products/steelstik-epoxy-putty-stick or Permatex Liquid Metal filler https://www.pepboys.com/permatex-specialized-maintenance-liquid-metal-filler/product/8066510 these work really well you can get them almost anywhere Walmart auto parts stores hardware stores just a couple of $